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Object Overview
Before us is a Jaeger Pedestal Aneroid Barometer, manufactured approximately between 1955 and 1965 by the famous Franco-Swiss watchmaking company . The instrument bears the serial number and belongs to Jaeger’s characteristic line of high-quality mid-20th-century desktop measuring instruments, in which precision mechanics were combined with expressive modernist design. The instrument itself is marked , while the dial bears the inscription , indicating that it was manufactured by the French side of the enterprise. In addition to measuring atmospheric pressure, the barometer is equipped with an integrated and, most notably, an exceptionally convenient system for correcting its readings according to the altitude of the place of installation above sea level. This system allows the instrument to be adjusted to the local altitude in a single movement, after which atmospheric pressure reduced to sea level can be read directly.
9039
self-elastic capsule movement
aluminium, brass, glass, phosphor-bronze, steel
The case of the instrument consists of a large circular brass rim mounted vertically on a low, round pedestal base. The overall composition is extremely restrained, giving the instrument an appearance that is simultaneously technical and decorative. The brass surface has a characteristic longitudinal finish that effectively emphasises the geometry of the case.
The front is protected by a flat mineral glass. At the centre of the glass is a knurled rotary knob used to position the trend-indicator hand. This hand serves to record a previous pressure reading and thus allows subsequent rises or falls in atmospheric pressure to be assessed visually — the classic principle of a barometric trend indicator. On the inside, the bezel is lined with a flexible metallic strip with a fine wire or mesh-like structure and a golden reflective tone, forming a decorative and functional reflecting ring.
Behind the glass is a large silver-grey metal dial. Immediately behind it is a metal rear plate, painted on its outer surface in a golden colour intended to imitate brass. The central area of the back is occupied by a projecting black cylindrical housing containing the aneroid mechanism itself. Below it is a separate smaller cylindrical housing for the thermometer. Thus, despite the very shallow overall profile of the instrument, its principal mechanical assemblies project rearwards and are arranged as compact, self-contained units.
The dial is particularly remarkable for its unusually high density of information. Within a relatively limited area, three concentric scales are arranged in succession — two barometric scales and one altitude scale.
The outermost and visually most prominent barometric scale is graduated in millimetres of mercury, covering a range of approximately 700 to 820 mmHg. Large numerals are positioned close to the edge of the dial and remain clearly legible even from some distance. Along the inner edge of this scale are traditional French weather indications: TEMPÊTE, PLUIE OU VENT, VARIABLE, BEAU TEMPS, and TRÈS SEC. Such inscriptions do not constitute an independent weather forecast in the strict meteorological sense, but rather represent the traditional interpretation of pressure zones commonly found on domestic aneroid barometers.
The next concentric scale presents the same atmospheric-pressure values in the metric unit widely used in mid-20th-century meteorology — millibars. It covers a range of approximately 940–1090 mbar. The user could therefore work either with the traditional millimetres-of-mercury scale or with millibars without the need for any conversion.
The innermost scale is not barometric but altimetric. It is graduated from approximately –50 to +1500 metres and is intended to compensate for the effect of the absolute altitude at which the instrument is used. This is one of the most interesting features of the design.
The rear of the black mechanism housing carries instructions in French explaining the adjustment procedure. To set the instrument, the user simply rotates the entire projecting housing of the aneroid mechanism until a special red index is aligned with the corresponding local altitude on the innermost scale. The barometer then indicates atmospheric pressure reduced to sea level.
In other words, the user does not need to calculate a correction manually or consult conversion tables: the mechanical system itself alters the relative position of the mechanism and the scale according to the selected altitude. For a domestic desktop instrument, this is a particularly elegant and practically effective solution.
Such correction has considerable practical value. Atmospheric pressure naturally decreases with altitude, so an ordinary barometer installed, for example, at 500 or 1000 metres above sea level will consistently indicate a lower absolute pressure than the same instrument located near sea level. The Jaeger system allows the local altitude to be taken into account in advance, thereby providing an approximate sea-level pressure, which is considerably more useful for assessing the synoptic situation.
In the lower part of the main dial is a small circular bimetallic thermometer, set within its own brass bezel but without an additional glass cover. Its scale is graduated in degrees Celsius from approximately –20 to +60 °C. Despite its modest size, the thermometer is harmoniously incorporated into the composition of the principal dial and transforms the instrument from a simple barometer into a compact desktop meteorological station.
The hand system further reflects the instrument’s watchmaking origins. The indicating elements are executed with considerable delicacy and precision; the main barometer hand and the thermometer hand are made of blued steel, whose deep blue-black tone contrasts effectively with the silvered surface of the dial. The manually adjustable reference hand has a decorative sword-shaped form and is intended to be positioned relative to the current location of the working barometer hand.
At the heart of the barometric mechanism is a large corrugated aneroid capsule made from an elastic copper alloy — most probably beryllium bronze or phosphor bronze, materials traditionally used for precision instruments in the mid-20th century. The capsule is partially evacuated, so changes in external atmospheric pressure produce an extremely small but stable movement of its upper diaphragm, while the lower part remains fixed to the base.
This movement is transmitted through a pivoting lever and pushrod to a toothed sector — effectively a short curved rack — which engages with a small pinion mounted on the hand arbor. Owing to the substantial mechanical transmission ratio, the minute movements of the aneroid capsule are converted into clearly visible angular displacement of the hand across the large dial. A return hairspring maintains constant tension within the transmission, reduces backlash in the gear engagement, and contributes to the stability of the indication.
The mechanism itself is exceptionally compact. The aneroid capsule occupies most of its diameter, while above it is a rigid metal frame carrying the hand arbor, lever transmission, toothed sector, and hairspring. The construction is not excessively complicated, yet the quality of the component finishing and the carefully considered arrangement are entirely consistent with the origins of the instrument in a company specialising above all in high-precision watchmaking. Unfortunately, there is no confirming evidence that the company manufactured the sensitive elements and their transmission system entirely in-house.
The Jaeger Pedestal Aneroid Barometer is a successful example of how the traditional aneroid barometer could be reinterpreted in the mid-20th century in accordance with a modern instrument aesthetic. Its restrained circular brass case, pedestal base, silvered multi-scale dial, blued hands, and small integrated thermometer create the characteristic appearance of a high-quality desktop instrument of its period.
Its significance, however, lies not only in its external design. The two pressure scales, altitude scale, and especially the original mechanical system for reducing the readings to sea level make this barometer considerably more functional than most decorative desktop aneroids of its time. It particularly well reflects the approach associated with Jaeger-LeCoultre: the combination of precision mechanics, a practical engineering concept, and carefully considered design within a comparatively simple domestic instrument.